PURPOSE: A highly efficient sludge treating apparatus and a method for the same are provided to make a profit by selling power generated from a methane engine generator and a steam generator. CONSTITUTION: A highly efficient sludge treating apparatus includes the following steps: sludge, food waste, leachate are uniformly treated(S1); the treated product is supplied by being pressurized at a pressure more than the critical pressure of water(S2); the treated product is subcritically heated at a temperature more than the critical temperature of the water to decompose organic biomass tissues in the treated product(S3); the treated products is heat-exchanged with fluid of a subcritical state(S4); a part of heat included in the fluid is collected to generate steam when the heat-exchanged fluid moves, and a steam boiler operates using the steam(S5); supernatant, organic materials, and inorganic materials are separated from fluid through a steam boiler(S6); the separated organic materials are stored, and an anaerobi
